@mixin flex($jc: center, $ai: center) {
    display: flex;
    justify-content: $jc;
    align-items: $ai;
}
@mixin center (){
    width: 1280px;
    height: 42px;
    margin: 0 auto;
}
@mixin tran($p: all, $t: 1s, $d: 0s, $tf: linear) {
    -webkit-transition: $p $t $d $tf;
    -moz-transition: $p $t $d $tf;
    -ms-transition: $p $t $d $tf;
    -o-transition: $p $t $d $tf;
    transition: $p $t $d $tf;
}
@mixin input(){
    outline: none;
    border: none;
}
@mixin but(){
        width: 800px;
        height: 52px;
        border: 1px solid #1b1b1b;
        background-color: #fff;
        margin: 20px auto;
        margin-left: 240px;
        font-size: 15px;
        font-weight: bolder;
        cursor: pointer;
        &:hover{
            color: #666;
        }
}
@mixin  li() {
    border-right:1px solid #dbdbdb;
    &:nth-child(1){
        border-left:1px solid #dbdbdb;
    }
}
